Chunk Header Incorporating Binary Flags and Correlated Variable-Length Fields

ABSTRACT

Playback and distribution systems and methods for multimedia files are provided. The multimedia files are encoded with flags associated with the content data of the multimedia files. Through the use of the flags, playback of the content is enhanced without significantly increasing the file size of the multimedia file.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.60/988,622, filed Nov. 16, 2007, the disclosure of which is incorporatedherein by reference.

BACKGROUND

The present invention relates generally to multimedia files and morespecifically to multimedia containers and systems for encoding anddecoding multimedia containers.

A multimedia engagement typically entails the decoding and presentationof audio, video, and subtitle information in a synchronized manner. Ingeneral, each one of the individual parts making up the presentation ispreviously encoded as a separate elementary stream and is thenmultiplexed together in an encapsulating container. TheAudio-Video-Interleave (AVI) container specified by MicrosoftCorporation of Redmond, Wash. is one such encapsulation format, and isalso one of the most prevalent forms of distributing standard-definitiondownloadable content on the Internet and peer-to-peer networks. TheMatroska (MKV) container specified by a group of Open-source Enthusiastsand published by Core Codec is another such encapsulation format, and isalso one of the most prevalent forms of distributing high-definitiondownloadable content on the Internet and peer-to-peer networks.

At its most basic level, the AVI container is made up of chunks andlists, each of which start with a four-character code (32-bit)identifier followed by a size indicator (32-bit) for that particularsection. AVI lists generally contain information about the file andencapsulate other chunks, where the chunks are typically used toencapsulate the elementary audio, video, and subtitle data streams. Atypical AVI chunk is illustrated in FIG. 1. The AVI chunk 10 includes afour-character code identifier 12, a size indicator 14 and chunk data.The character code identifier can be expressed in the form nnxx, wherenn is a stream number and xx is the stream designator.

The AVI container specification includes two mandatory lists, whichdefine the format of the streams and the stream data, respectively. AVIcontainers can also include an index chunk, which gives the location ofdata chunks within an AVI container. An AVI container with thesecomponents has the following form:

RIFF(‘AVI’ LIST('hdrl' ...) LIST('movi' ...) ['idx1' (<AVI Index>)] )

A decoder typically decodes multimedia information contained within anAVI container by parsing the ‘hdrl’ list to obtain information about theelementary streams contained within the AVI container. Once the ‘hrdl’list has been parsed, the multimedia information can be rendered fromthe start of the ‘movi’ list. The ‘idx1’ chunk can be used to perform,so called “trick play”, functions such as seeking, rewinding or fastforwarding. Information contained within the ‘idx1’ chunk can be used bya player to locate chunks containing multimedia information sought by atrick play function.

At its most basic level, the MKV container is made up of elements, withmost elements able to nest some other elements. FIG. 1B illustrates sucha typical MKV container. The element type is defined by avariable-length integer identifier and the element's size by avariable-length integer size field, followed by the corresponding databytes whose length is determined by the size field. The container hasstandard element types that can be used to carry a variety of payloads,such as headers 17, bit streams 18, different types of indexes (e.g.,segment and track indexes 13, 15) and auxiliary data 19.

SUMMARY

Embodiments of the invention utilize a modified form of the AVI chunkheader that incorporates one or more bit-level flags and zero or moredata fields, the content of which are indicated by the flag settings.Embodiments also utilize a series of newly introduced element types,with new element identifiers of the MKV container, that incorporate zeroor more data fields, the content of which are indicated by the elementidentifier. Each new flag of AVI, new element of MKV or similar newaddition to a container format and the data field(s) have a pre-definedmeaning, such that when interpreted correctly may provide a new featureto multimedia systems. The flags and data fields are extensible toincorporate new features as required. In many embodiments, the flagsenable the playing of content within a chunk and/or performance of trickplay functions and other functionality without the need to obtaininformation from elsewhere in the container. Trick play functions arefunctions that involve playing portions of a multimedia sequence in anon-sequential fashion. For example, functions such as fast forward andrewind involve achieving the appearance that the multimedia sequence isplaying at a specified speed by skipping frames. Other trick playfunctions can include, but are not limited to, skipping between chaptersand/or scenes defined within a multimedia sequence.

In one embodiment, a method of playing back content by a playback devicestored in a media file supplied by a media server. The method comprisesproviding a media file having content data and header, the content datahaving a plurality of media frames and the header having a plurality offlags or elements; decoding the content data by a playback device;displaying content on a display screen from the decoded content data;receiving a user request; identifying a flag or element from theplurality of flags or elements based on the received user request; anddecoding one or more media frames from the subset of the plurality ofmedia frames based on the identified flag or element.

In another embodiment, a playback device for decoding a media file isprovided. The device comprises a de-multiplexer arranged to receive anddecipher a media file having content data and a header having aplurality of flags or uniquely defined elements. The device alsocomprises a video decoder coupled to the de-multiplexer and arranged toreceive video portions of the deciphered media file and an audio decodercoupled to the de-multiplexer and arranged to receive audio portions ofthe deciphered media file. The de-multiplexer selects the video portionsand the audio portions to be transmitted to the respective video andaudio decoder based on the plurality of flags or uniquely definedelements from the deciphered media file.

The above-mentioned and other features of this invention and the mannerof obtaining and using them will become more apparent, and will be bestunderstood, by reference to the following description, taken inconjunction with the accompanying drawings. The drawings depict onlytypical embodiments of the invention and do not therefore limit itsscope.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a conceptual illustration of the data in anAudio-Video-Interleave (AVI) container.

FIG. 1B is a conceptual illustration of the data in a Matroska (MKV)container.

FIG. 1C is a conceptual illustration of data in a generic container.

FIG. 2A is a conceptual illustration of data within a chunk inaccordance with an embodiment of the invention.

FIG. 2B is a conceptual illustration of data within a modified containerformat in accordance with one embodiment of the invention.

FIG. 2C is a conceptual illustration of data within an element inaccordance with one embodiment of the invention.

FIG. 3 is a conceptual illustration of a chunk in accordance withanother embodiment of the invention that includes a mandatory sizefield.

FIGS. 4A and B are conceptual illustrations of chunk headers includingchunk size information and time stamp information in accordance withembodiments of the invention.

FIG. 5 is a conceptual illustration of flags and corresponding datafields that can be included in a chunk header in accordance with anembodiment of the invention.

FIG. 6 is a conceptual illustration of frame packing of B frames in aconventional AVI container.

FIG. 7 is a conceptual illustration of a frame sequence including Bframes in a container in accordance with an embodiment of the invention.

FIG. 8 is a conceptual illustration of key frame references containedwithin the chunk headers in accordance with embodiments of theinvention.

FIG. 9 a is a conceptual illustration of content filtering informationcontained within the chunk headers of chunks of multimedia informationcontained within a container in accordance with an embodiment of theinvention.

FIG. 9 b is a conceptual illustration of highlight information containedwithin the chunk headers of chunks of multimedia information containedwithin a container in accordance with an embodiment of the invention.

FIG. 9 c is a conceptual illustration of alternate segment informationcontained within the chunk headers of chunks of multimedia informationcontained within a container in accordance with an embodiment of theinvention.

FIG. 10 is a semi-schematic illustration of a content player inaccordance with an embodiment of the invention.

FIG. 11 is a semi-schematic network diagram of progressive playbacksystem in accordance with an embodiment of the invention.

FIG. 12 is a flowchart of a process utilizing chunk information within amultimedia file in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

Turning now to the drawings, multimedia containers in accordance withembodiments of the invention that include chunks with headers containingflags and data fields that describe data within the chunk are shown. Inseveral embodiments, the chunk headers include a series of flags anddata fields, where the flags indicate the nature of the informationcontained in the data fields. In many embodiments, the flags and datafields enable simplification of the decoding of the multimediainformation contained within the container. In a number of embodiments,a player need not obtain an entire multimedia file in order to seekwithin the file, commence playing content, and/or perform trick play orother functions.

Containers in accordance with embodiments of the invention are typicallyvariations of the AVI, MKV or other similar container, such as shown inFIG. 1 c, and are composed of lists, chunks and/or elements. Thecontainer in FIG. 1 c includes a track header 17′, followed by aninterleaved bit-stream chunk 18′ and tracks' index data 15′. Tracks'index data 15′ is also incorporated in the interleaved bit-stream chunk18′. An auxiliary data 19′ follows the interleaved bit-stream. A chunkin accordance with an embodiment of the invention is shown in FIG. 2 a.The chunk 20 includes a chunk header that is made up of a character codeidentifier 22, a series of flags 24 and header data fields 26. The chunk20 also includes chunk data 28. The character code identifier 22 issimilar to that of a conventional AVI character code identifier in theform nnxx, where nn is a stream number and xx is the stream designator.

The flags can be structured in any of a variety of ways. In theillustrated embodiment, the flags are 8-bit flags. Each 8-bit flag maybe further subdivided into sub-flags, which are at least 1 bit wide, andmay hold specific significance for the current chunk and/or thefollowing or previous chunks. The sub-flags may also designate a seriesof follow-on data fields in the header data field 26, or alternativelyrefer to a data field stored in a separate section of the file. Thesub-flags may also be grouped into more than one bit, and may spanseveral 8-bit flags. One of the sub-flags may indicate a follow-on 8-bitflag, such that an infinite number of flags can be presented in thechunk header. The data in the first flag typically has a higherimportance and in general must be present for all chunks to operatecorrectly.

A set of header data fields 26 follows the flags. In a number ofembodiments, the size and number of header data fields 26 vary and theflags 24 indicate the composition of the header data fields. In otherembodiments, the header data fields 26 are a fixed size and theallocation of bits is indicated by the flags 24.

As discussed above, the chunk data 28 can contain any type ofinformation. Chunks that contain multimedia information, such as chunkswithin a ‘movi’ list of container modified in accordance with anembodiment of the present invention, contain information from one ormore of the elementary streams. In several embodiments, the flags 24 andthe header data fields 26 provide information concerning the nature ofthe chunk data and/or the manner in which the chunk data should behandled by a player.

Another container in accordance with an embodiment of the invention isalso shown in FIG. 2 b. Similar to that illustrated in FIG. 2 a, thecontainer includes a header 24″ that includes flags and data fields 23.In one embodiment, the flags and/or data fields 23 includes additionaltrack information regarding the tracks, e.g., a trick play track ormaster track (Tracks Data, Tracks Data Version, Tracks Data PayloadSize, Tracks Data Payload, Trick Track Unique Identifier, Trick TrackSegment Unique Identifier, Trick Track Flag, Master Track UniqueIdentifier, Master Track Segment Unique Identifier and a MediaDescription). Interleaved bit-stream chunks/blocks, data 28″, follow.Track index data 29, auxiliary data 27 and segment index 25 are alsoincluded and in one embodiment provide information similar those foundin a standard container. In other embodiments, the track index data 29includes or is entirely composed of hierarchical index information 29 aand the interleaved bit-stream chunks include DRM and Seek (Forward andBackward) information 21 (DRMInfo, Previous Offset, Next Offset,Previous Time Code) discussed in greater detail below. The Hierarchicalindex information includes elements of a Hierarchical Index withHierarchical Index Points, Time, Track and Position). The hierarchicalindex information and use thereof are described in greater detail inU.S. Provisional Application No. 60/988,513, filed Nov. 16, 2007 and thecorresponding non-provisional application entitled “Hierarchical andReduced Index Structures for Multimedia files”, filed Nov. 17, 2008 thatclaims the benefit of the provisional application. The entiredisclosures of these applications are hereby incorporated by referenceas if set in full herein.

In one embodiment, the forward/backward, hierarchical index, DRM andother similar features are introduced as elements into the container. Anexample of such an element is shown in FIG. 2C. The element includes anelement identifier 31, payload size 33 and a payload 35, each of whichhave variable lengths (variable number of bytes), but the payload lengthis based on the value of the payload size 33. Examples of the elementidentifiers are provided in the following tables.

DRM RELATED IDENTIFIERS ELEMENT_TRACKSDATA_ID 0xDAELEMENT_TRACKSDATA_VER_ID 0xDB ELEMENT_TRACKSDATA_PSIZE_ID 0xDCELEMENT_DRMINFO_ID 0xDD ELEMENT_TRACKSDATA_PAYLOAD_ID 0xDE

TRICK PLAY TRACK IDENTIFIERS ELEMENT_ENHANCEDTRACK_UID_ID 0xC0ELEMENT_ENHANCEDTRACK_SEGUID_ID 0xC1 ELEMENT_ENHANCEDTRACK_FILENAME_ID0xC2 ELEMENT_MASTERTRACK_SEGUID_ID 0xC4 ELEMENT_MASTERTRACK_FILENAME_ID0xC5 ELEMENT_ENHANCEDTRACK_FLAG_ID 0xC6 ELEMENT_MASTERTRACK_UID_ID 0xC7

PREVIOUS AND NEXT REFERENCE FRAME IDENTIFIERSELEMENT_PREVIOUS_REF_FRAME_ID 0xC8 ELEMENT_PREVIOUS_REF_FRAME_OFFSET0xC9 ELEMENT_PREVIOUS_REF_FRAME_TIMECODE 0xCA ELEMENT_NEXT_REF_FRAME_ID0xCB ELEMENT_NEXT_REF_FRAME_OFFSET 0xCC ELEMENT_NEXT_REF_FRAME_TIMECODE0xCD

HIERARCHICAL INDEX IDENTIFIERS ELEMENT_HIERARCHICAL_INDEX_ID 0x2AD1D3ELEMENT_HIERARCHICAL_INDEX_POINT_ID 0x30A1D9ELEMENT_HIERARCHICAL_INDEX_TIME_ID 0x4A10ELEMENT_HIERARCHICAL_INDEX_POSITIONS_ID 0x4A11ELEMENT_HIERARCHICAL_INDEX_TRACK_ID 0x4A12ELEMENT_HIERARCHICAL_INDEX_CUEPOS_ID 0x4A13

Utilizing the element identifier 31 similar to the flags and the payload35 similar to the data fields, a playback device can identify and decodethe appropriate data to implement the desired features, e.g.,forward/backward content filtering etc. For example, in one embodiment,an element identifier 31 is read and recognized by the playback device.The media file is read or parsed to match a sequence against the tableof valid element IDs. Once recognized, i.e., a match, the elementlocated and processes up to the size of the payload as provided by thepayload size 33.

In operation, the flags, data fields and elements included in theheaders or interleaved in the bit stream in accordance with embodimentsof the invention can provide a player attempting to decode the chunkwith information concerning the data located within the chunk. The moredetailed the information provided in the header, the less informationthat the player must obtain from elsewhere in the file to playmultimedia information contained within the chunk. In this way, theheaders in accordance with embodiments of the invention can reduce thevolume of data that a player must obtain from a multimedia file in orderto perform functions such as seeking to a point within the multimediafile, playing multimedia information from an arbitrary point within amultimedia file and/or performing trick play functions with respect tomultimedia content contained within a multimedia file. Examples ofspecific pieces of information that can be included in headers inaccordance with embodiments of the invention to assist players in thedecoding of chunk data are discussed further below. It should be notedthat for the AVI container format and/or other similarly structuredformats, bit-wise flags and associated data fields are incorporated intonew or existing chunks. For the MKV container format and/or othersimilar types, new elements with unique identification fields, sizeand/or data fields are added to the bit stream.

Size

A conventional AVI chunk header includes a field that containsinformation concerning the size of the chunk. A static field is one wayof representing size information. A chunk header in accordance with anembodiment of the invention that includes such a size value field 30 isshown in FIGS. 3 and 4 b. In other embodiments, other representationscan be used that utilize bits within the flags (i.e., sub-flags) tosupport variations in the size value field. A chunk header in accordancewith an embodiment of the invention that includes a size value field 41that can itself vary in size is shown in FIG. 4 a. In many embodiments,the flags in a chunk header contain a first bit that indicates whetherthe size of the chunk is stored as fixed numbers in a different segmentof the file, or alternatively if the size is contained within the headerdata fields following the flags. Two additional bits can indicate alook-up index for fixed numbers, or the number of bytes used when anactual size value is represented. Indexing to fixed numbers within thechunk header to represent the size of a chunk can significantly reduceoverhead when a series of chunks are the same size, such as chunkscontaining a constant bit rate elementary stream. In other embodiments,any number of sub-flags can be used to indicate one of a variety ofdifferent configurations of the size value field.

Timestamp

A conventional AVI chunk header does not typically include a time stamp.As a result, a player often must rely heavily on the index containedwithin an AVI container in order to locate corresponding audio, videoand/or subtitle chunks. Including time stamp information in a chunkheader in accordance with an embodiment of the invention can enableplayers to locate corresponding audio, video and/or subtitle chunkswithout reference to an index. In addition, the existence of a timestampcan aid in a synchronized presentation in case of errors present in thefile due to transmission or storage problems. Both the chunk headerstructures shown in FIGS. 4 a and 4 b are examples of chunk headers inaccordance with embodiments of the invention that include a data field40 containing time stamp information.

In many embodiments, time stamp information is mandatory and a sub-flagindicates whether or not the time stamp information is truncated 40 a orabsolute 40 b. The truncated time stamp may have a resolution that issmaller than the absolute timestamp, thus allowing fewer bits to be usedat the cost of tighter requirements on the synchronization ambiguity.Hence if the truncated timestamp is 16-bits wide and is in the units ofmilliseconds, it may at most represent a time value of 65.535 seconds,while if in the units of 1/90,000, the 16 bits allow for a resolution ofonly 0.728 seconds. In the latter case, the maximum distance betweencorresponding audio and video samples must be less than half of 0.728seconds; otherwise, it will be impossible to unambiguously determine therelationship between the corresponding audio and video packets. Thus, inthe case where a truncated time stamp is used it is important to ensurethat any uncertainties in the synchronization remain below the maximumvalue that can be expressed by an associated truncated time stamp.Likewise the absolute timestamp may have a resolution of at least 32bits or larger, and may represent the maximum amount of time from thestart of an AVI chunk to the last chunk in a contiguous moviepresentation. The timescale for both timestamp representations may bepre-determined, or alternatively specified in a separate section of thefile.

Flags

Although the embodiments shown in FIGS. 4 a and 4 b include two flagfields, many embodiments of the invention include multiple sub-flags andpotentially multiple data fields. Flags and data fields that can beincluded in chunk headers in accordance with an embodiment of theinvention are shown in FIG. 5. The flags 26 include a plurality ofsub-flags, each of which provides information concerning chunk dataand/or header data fields 28. The sub-flags relating to Absolute-FixedSize, Fixed Size Index/Byte Numbers, Timestamp (truncated/absolute) havebeen described above. Additional flags that can form part of a chunkheader include Duration (none/present), Presentation Number, RequiresReference Packing (none/present), flags EXTENSION, DRM Packet(none/present), New Configuration Flag (none/fixed/lookup/inline),Forward Access Key Frame Offset (key), Backward Access Key Frame Offset(key), Content Filtering (none/present), Frame Metadata (none/present),and flags EXTENSION. These flags are discussed below. Although aspecific set of flags and associated data fields is shown in FIG. 5,other sets of flags and/or data fields can be used in accordance withembodiments of the invention. In particular, any flag and/or data fieldcan be included in a chunk header in accordance with an embodiment ofthe invention that provides a player with information concerning thedecoding of a chunk that the player would otherwise have been requiredto obtain from another chunk had a conventional AVI chunk header beenused.

Duration Sub-Flag

The Duration sub-flag signals the availability of a duration data fieldin the header-data, determining the amount of time a chunk should bepresented after decoding. This value is typically equal to thedifference between the timestamp of two consecutive chunks, except incertain cases where the streams are non-continuous (such as subtitles ormeta-data). The duration may be in the same timescale as the timestampvalues, and may have a predetermined value that is typically 8, 16, 24or 32 bits in size, but may be of a different size.

It should be noted that Duration, Size and Timestamp information asdescribed above may not be needed in all container formats, e.g., MKV,may already include implementations to supply the appropriateinformation. However, such implementations are specific to the containerformat and/or static. As such, unlike utilizing bits within flags tosupport variations in a data field, those implementations may not beextensible to apply to multiple and varied types of container formats oralternatively may use other means of incorporating new elements in anexisting specification.

Packing Reference Frame Flags

The two flags, Presentation Number and Requires Reference Packing may beused in aiding with the packing of reference frames. It is a well-knownproblem that in cases where the decoder requires a one-frame-in,one-frame-out relationship, all the frames required for decoding apredicted frame must be supplied together to the decoding device. Inthose scenarios, one commonly used solution has been to group the framesas a packed frame and to follow this packed frame by empty or markerchunks (often designated as [ ]). A sequence of packed frames and markerchunks is shown in FIG. 6.

Instead of the traditional packing structure, here we provide for theuse of two stream markers termed “Presentation Number” 71 and “RequiresReference” 73. With the presence of these two stream markers, it ispossible to create a stream of single frames in each individual chunkand use these marker values in creating a representative packed framesequence for the special decoding scenarios. A sequence of frames, theordering of the frames in a container in accordance with an embodimentof the invention and chunk header information concerning presentationorder is shown in FIG. 7. The Presentation Number may be a numberspecifying the order in which the decoded chunk data should bepresented, and can be 8, 16, 24, 32 or any number of bits. The RequiresReference sub-flag marks frames that require reference packing inscenarios that must support a one-frame-in, one-frame-out scenario. Thissub-flag may or may not have a corresponding value in the header datafields. The same sub-flags and packetization can be used to incorporateopen and closed GOP encapsulation. The important distinction between theuse of these sub-flags and the previously used reference packing streamsis that in this method, every frame will be individually stored and onlythe sub-flags may be used to infer a specific framing structure.

Forward and Backward Access Sub-Flags

The Forward and Backward Access (key) Frame Offset sub-flags 81,82indicate the presence of an offset field in the header-data section ofthe chunk header which provides a pointer to the previous and nextaccess or key-frame chunk. An access chunk is typically one which can bedecoded independently of any other chunks and generally serves as anaccess point during seek and trick-play operations. The offset may be arelative value from the current position of the pointer, oralternatively with a larger bit-field representation the offset can bean absolute one from the beginning of the file. A possible use case foraccess (key) frame offset pointers in accordance with an embodiment ofthe invention is illustrated in FIG. 8. The forward access flag 81directs a playback device to extract the forward access offset thatpoints to the next key frame. At the next key frame, a forward accessflag and offset data field provides a reference to the next key frame.As such, from each key-frame the playback device can seek or jump aheadto the next key frame utilizing only the forward access flag and offsetdata field. This accelerates trick-play/seek functions and reducesprocessor overhead of the playback since the playback device does nothave to traverse and/or decode the each entire chunk.

The inclusion of the flag and data field however increases the size ofthe media file. In one embodiment, the offset data field is storedinitially or progressively as the media file is played. Storing eachoffset data field prior to playback can slow the initial playback of themedia file, but also enhances trick-play functions and reduces overallprocessor time with the processing time to decode only the flag and datafield adding to the overall processor time. With reduced processoroverhead and immediate access to the next frame, playback of the contentappears visually smoother.

The backward flag 82 and offset data field is similar to the forwardflag 81 however the backward offset references to a previous key frame.However, it should be appreciated that in conventional playback devicesbackward or rewind functions can't be performed or are extremely limitedwithout retaining and/or decoding the entire media file. For example,after playing a portion of the media file, the portion is discardedbefore playing the next portion, and thus reversing direction requiresretrieving the previous portion and finding the previous key frame. Thisis also further limited by most container formats of the media file. Forexample, without a fixed size or a marker to the previous key frame, theplayback device has to decode the previous portion of the media file tofind the previous key frame. Furthermore, some consumer electronicdevices are not sophisticated and are thus not able to perform extensiveprocessing functions to retrieve, locate and decode the previous framewithin a user's desired wait time.

In one embodiment, similar to the flags above, the media file insteadincludes an element with a unique backward access identifier followed bya backward offset data field, e.g., within the payload data, that has apointer to a previous key-frame block, a value that corresponds to aprevious key-frame time code or timestamp, or an offset value calculatedrelative to a start position, e.g., at the beginning of the file orrelative to a frame being displayed. Likewise, a forward accessidentifier and forward offset data field can also be included thatpoints, provides a timestamp to the next key-frame, or an offset valuerelative to a start position. It should be appreciated that althoughflags and data fields are described throughout the application othersimilar types of advance identifiers such as unique element identifiersalong with the associated data fields or payload are also applicablebased on the container format of the media file desired or provided.

DRM and Metadata Flags

The DRM Packet and Frame Metadata sub-flags signal the presence ofinformation in the header data fields which identifies the data type,and is followed by a number of related bytes in the header data fields.The DRM Packet sub-flag signifies specific Digital Rights Management(DRM) data, which may be used in the decryption of the informationcontained in the chunk. Many previous implementations of DRM in thecontext of an AVI container have required DRM information to becontained in a separate chunk that is interleaved with the elementarystreams. In the embodiments described above, DRM information can beincluded in the chunk containing the frame (or other information) towhich it relates. The Frame Metadata sub-flag indicates the presence ofmetadata related to the frame contained within the chunk, which may beused in some form of identification and classification. The header datafields associated with the DRM Packet and Frame Metadata sub-flags canbe identified via a set of pre-determined rules, or alternatively may beidentified via specifications provided in a separate section of thefile. These concepts can likewise be added to the MKV specification bycreating new elements as part of an audio or video Block which is anequivalent of the chunk in the AVI container.

Other examples of utilizing metadata is described in U.S. Provisionalpatent application Nos. 61/059,547, filed Jun. 6, 2008, and 61/109,476,filed, Oct. 29, 2008, the disclosures of which are hereby incorporatedby reference as if set forth in full herein.

Content Filter Flags

The Content Filtering sub-flag indicates the presence of information inthe header-data section related to chunk-level content-filteringinformation. The content-filtering can apply to any circumstance where aportion of the content is to be selectively presented, anywhere up tothe entire length of the presentation. It can apply selectively to thedifferent streams in an overall presentation, where the behavior of thefiltering can be determined by a set of pre-defined rules. Thepresentation rules can define the behavior of the decoding device ineach case, such as muting an audio track, blackening the video track, orskipping a portion of the presentation altogether. In many embodiments,a 16-bit identifier in the header-data can be used to signal up to 16different types of content-filtering options for a particular chunk,although the field may be specified to have a larger value. Acorresponding header data field can indicate the level for each one ofthe 16 filtering modes. Some example filter types may be the following:

Identifier Mask Designation 0x1 Hierarchical, Inclusive 0x2Hierarchical, Exclusive 0x4 Alternate Segment 0x8 . . .

The primary use of chunk accurate content filtering is to addflexibility in presenting the same stream in a different form, based ona series of filtering levels and types. For example, the same contentmay be presented to adults, and a different version may be shown tochildren. A multimedia presentation containing content filteringinformation (original presentation 91, PG rating section 93, PG-13rating section 95, R rating section 97) in accordance with an embodimentof the invention is shown in FIG. 9 a. Alternatively, a presentation maycontain a shortened ‘highlight’ section, which will display only certainportions of the materials (highlight section 94). A multimediapresentation containing highlight filtering information in accordancewith an embodiment of the invention is shown in FIG. 9 b. A presentationmay also contain alternate segments, which can be shown in place of oneanother. A multimedia presentation including alternate segments (defaultsegment 96, alternate segment 98) indicated in accordance with anembodiment of the invention is shown in FIG. 9 c.

All of the content-filtering scenarios described above can apply to thesame stream. In many embodiments, up to 16 different filtering modes canbe defined with overlapping functionality; hence, more than onefiltering mode could be specified per chunk in which case the differentlevels follow the order of the bit-field sub-flag. Each mode can have atleast one byte defining its level. The definition of the level and itsdesignation may be either previously specified or alternativelydescribed in a different segment of the container. Other examples ofutilizing content filtering is described in U.S. Provisional Patentapplication Nos. 61/059,547, filed Jun. 6, 2008, and 61/109,476, filed,Oct. 29, 2008, filed, the disclosures of which are hereby incorporatedby reference as if set forth in full herein.

New Configuration Sub-Flag

The New Configuration sub-flag is a 2 bit flag representing a newconfiguration for the decoding operation of the current chunk and allsubsequent chunks. The sub-flag can indicate the presence of an index,which selects a particular configuration from a list of previouslydefined values or alternatively from parameters defined separately in adifferent segment of the file. Alternatively, the flag may indicate thepresence of actual configuration information in the header-data that canspecifically describe the features of the stream such that a decoder isable to successfully decode and present the information in asynchronized manner. Using a list of previously defined values requiresanalyzing a large number of presentation streams and selecting the mostcommon configurations for each track. This pre-determined list ofconfigurations can be published separately and selected via theConfiguration Index parameter in the header-data. The signaling of a NewConfiguration in the same manner can be incorporated into the MKVcontainer by defining a new element which defines the same structure asdescribed above.

Extension Sub-Flag

The flags EXTENSION sub-flags can be used to indicate that additionalbytes of flags are included in the chunk header. In other embodiments,other techniques can be used to indicate the presence of additionalflags. Although specific sub-flags are outlined above, other typesand/or combinations of sub-flags can be included in flags of a chunkheader in accordance with embodiments of the invention that provideinformation concerning a chunk to a player.

In general, the use of flags and corresponding data create anoptional-inclusion approach which can help keep the overhead ofadditional features very small while at the same time allow for theirinclusion where and if necessary. It is important to note that whilethis disclosure has described a specific relationship between the flags,sub-flags, header data fields, and supplemental data appearing in theAVI chunk header, the chunk header is generally expandable in accordancewith embodiments of the invention using these components.

A player configured to decode a multimedia presentation formatted inaccordance with an embodiment of the invention is illustrated in FIG.10. The player 100 retrieves chunks of information from files containingmultimedia presentations that are stored on a storage media 102 using afront end controller 104. The chunks are provided to a demultiplexer 106that processes the file and has the capability of deciphering specificinformation about a container (the AVI & MKV containers being examplecontainers capable of being deciphered by the multiplexer). Thedemultiplexer deciphers the container information and separates thevarious components and transfers them to their appropriate decoder unit.Chunks that form part of the elementary streams are directed to queueswhere the chunks are held pending decoded by decoders 108. The decodedchunk data is provided to synchronization circuitry 110, which ensuresthat the elementary streams are synchronized prior to their output byoutput devices 112 for rendering by a display device such as atelevision or a computer monitor 114. In many embodiments, thedemultiplexer conveys timing information extracted from chunk headers tothe synchronization circuitry to enable synchronized playback of thedecoded information. As discussed above, the information provided to theplayer by the flags and header data fields in each chunk can enable thedemultiplexer to make a number of decisions concerning the queuing anddecoding of chunk information without reference to other chunks withinthe multimedia file. In players that read multimedia information fromfixed media or that request information via a network, obtaininginformation from various locations within a file can be cumbersome andthe presence of required information within a chunk can reduce latencywithin the player.

Referring now to FIG. 11, a progressive playback system in accordancewith an embodiment of the invention is shown. The progressive playbacksystem 190 includes a media server 192 connected to a network 194. Mediafiles are stored on the media server 194 and can be accessed by devicesconfigured with a client application. In the illustrated embodiment,devices that access media files on the media server include a personalcomputer 196, a consumer electronics device such as a set top box 18connected to a playback device such as a television 200, and a portabledevice such as a personal digital assistant 202 or a mobile phonehandset. The devices and the media server 192 can communicate over anetwork 194 that is connected to the Internet 204 via a gateway 206. Inother embodiments, the media server 192 and the devices communicate overthe Internet.

The devices are configured with client applications that can requestportions of media files from the media server 192 for playing. Theclient application can be implemented in software, in firmware, inhardware or in a combination of the above. In many embodiments, thedevice plays media from downloaded media files. In several embodiments,the device provides one or more outputs that enable another device toplay the media. When the media file includes an index, a deviceconfigured with a client application in accordance with an embodiment ofthe invention can use the index to determine the location of variousportions of the media. Therefore, the index can be used to provide auser with “trick play” functions. When a user provides a “trick play”instruction, the device uses the index to determine the portion orportions of the media file that are required in order to execute the“trick play” function and requests those portions from the server. In anumber of embodiments, the client application requests portions of themedia file using a transport protocol that allows for downloading ofspecific byte ranges within the media file. One such protocol is theHTTP 1.1 protocol published by The Internet Society or BitTorrentavailable from www.bittorrent.org. In other embodiments, other protocolsand/or mechanisms can be used to obtain specific portions of the mediafile from the media server.

Referring to FIG. 12, one embodiment of a process of utilizing the chunkand flag structure is shown. A media file is received from, for example,a media server based on a media file request from a playback device orin particular a playback engine of the playback device (111). Uponlocating the requested media file, the media server transmits all orsome portions at a time of the media file to the playback device. Theplayback device in one embodiment decodes the transmitted media file tolocate the header portion of the media file (112). The located headerportion is decoded to identify flags and/or associated data fieldswithin the header portion (113). In one embodiment, the flags and/orassociated data fields are stored or cached into memory to facilitateaccess to the flags and/or data fields (114). The media file is decodedand displayed based on the flags and/or data fields identified (115). Ifthere is a user request (116), e.g., a forward seek request, theassociated flag and/or data fields are located and/or retrieved fromstorage (117). Based on the flags and/or data fields, portions of themedia file are located and/or displayed to comply with a user requestreceived by the playback device (115). The process continues untilterminated by the user.

While the above description contains many specific embodiments of theinvention, these should not be construed as limitations on the scope ofthe invention, but rather as an example of one embodiment thereof.Accordingly, the scope of the invention should be determined not by theembodiments illustrated, but by the appended claims and theirequivalents.

1. A method of playing back content by a playback device stored in amedia file supplied by a media server, comprising: providing a mediafile having content data and header, the content data having a pluralityof media frames and the header having a plurality of flags or elements;decoding the content data by a playback device; displaying content on adisplay screen from the decoded content data; receiving a user request;identifying a flag or element from the plurality of flags or elementsbased on the received user request; and decoding one or more mediaframes from the subset of the plurality of media frames based on theidentified flag or element.
 2. The method of claim 1 wherein the headerfurther comprises a plurality of data fields and wherein the pluralityof flags and data fields of the header references portions of thecontent data.
 3. The method of claim 1 wherein the plurality of flagsare ordered from highest importance to lowest importance.
 4. The methodof claim 1 wherein the plurality of elements each contain a uniqueidentification field, size and data fields.
 5. The method of claim 4wherein at least one unique identification field corresponds to aforward access identifier and at least one data field follows theforward access identifier and includes a forward offset data fieldhaving a offset value relative to a position of a frame being displayedor a start point of the media file.
 6. The method of claim 4 wherein atleast one unique identification field corresponds to a backward accessidentifier and at least one data field follows the backward accessidentifier and includes a backward offset data field.
 7. The method ofclaim 6 wherein the backward offset data field has a pointer to aprevious key-frame block.
 8. The method of claim 6 wherein the backwardoffset data field has a value corresponding to a previous key-frame timecode.
 9. The method of claim 2 wherein the plurality of flags include aforward access flag and the plurality of data fields include a forwardoffset data field, the forward access flag referencing the forwardoffset data field.
 10. The method of claim 2 wherein the plurality offlags include a backward access flag and the plurality of data fieldsinclude a backward offset data field, the backward access flagreferencing the backward offset data filed.
 11. The method of claim 9wherein the forward offset data field has a pointer to a next key-framechunk, the next key-frame chunk arranged to be decoded independently ofany other chunks and providing an access point during trick-playoperations.
 12. The method of claim 11 wherein the pointer is an offsetvalue calculated from a position of a frame being displayed.
 13. Themethod of claim 9 wherein the forward offset data field defines abit-field representation relative to a start point in the media file.14. The method of claim 2 wherein each flag of the plurality of flagshas a one to one corresponding reference to each data field of theplurality of data fields.
 15. The method of claim 2 wherein theplurality of flags and the plurality of data fields include informationlocated within a chunk in the content data.
 16. The method of claim 14further comprising decoding the chunk in which at least one flag of theplurality of flags is decoded.
 17. The method of claim 16 furthercomprising bypassing decoding of a remainder of the chunk based on thedecoded flag.
 18. The method of claim 17 further comprising bypassingdecoding of a portion of the chunk based on the decoded flag.
 19. Themethod of claim 16 further comprising decoding only a portion of thechunk based on the decoded flag.
 20. The method of claim 16 furthercomprising decoding another chunk within the media file based on thedecoded flag.
 21. The method of claim 19 wherein the decoded flagreferences a data field of the plurality of data fields that pointsdirectly to a particular media frame of the content data.
 22. The methodof claim 4 further comprising decoding the chunk in which at least oneelement of the plurality of elements is decoded.
 23. The method of claim22 further comprising bypassing decoding of a remainder of the chunkbased on the decoded element.
 24. The method of claim 22 furthercomprising bypassing decoding of a portion of the chunk based on thedecoded element.
 25. The method of claim 22 further comprising decodingonly a portion of the chunk based on the decoded element.
 26. The methodof claim 22 further comprising decoding another chunk within the mediafile based on the decoded element.
 27. The method of claim 22 whereinthe decoded element references a data field of the plurality of datafields that points directly to a particular media frame of the contentdata.
 28. A playback device for decoding a media file, the devicecomprising: a de-multiplexer arranged to receive and decipher a mediafile having content data and a header having a plurality of flags oruniquely defined elements; a video decoder coupled to the de-multiplexerand arranged to receive video portions of the deciphered media file; anaudio decoder coupled to the de-multiplexer and arranged to receiveaudio portions of the deciphered media file; wherein the de-multiplexerselects the video portions and the audio portions to be transmitted tothe respective video and audio decoder based on the plurality of flagsor uniquely defined elements from the deciphered media file.
 29. Thedevice of claim 28 further comprising: a storage media storing the mediafile; and a controller coupled to the storage media and arranged toretrieve the media file from the storage media based on a user requestand transmit to the media file to the de-multiplexer.
 30. The device ofclaim 29 further comprising a synchronization circuitry coupled to thevideo and audio decoders, the video and audio decoders decodingrespective video and audio chunk data and supplying the decoded videoand chunk data to the synchronization circuitry.
 31. The device of claim30 wherein the de-multiplexer extracts timing information from theplurality of flags or uniquely defined elements from the decipheredmedia file and supplies the timing information to the synchronizationcircuitry, the synchronization circuitry synchronizing playback of thedecoded video and chunk data from the video and audio decoders based onthe supplied timing information.
 32. The device of claim 31 wherein theplurality of flags or uniquely defined elements include a forward accessflag or unique element and the media file includes a plurality of datafields having a forward offset data field, the forward access flag orunique element referencing the forward offset data field, the forwardoffset data field having a pointer to a key-frame chunk and accessibleby the de-multiplexer.
 33. The device of claim 32 wherein thede-multiplexer supplies the key-frame chunk to the video and audiodecoders to be decoded independently of any other chunks based on thepointer from the forward offset data field.
 34. The device of claim 31wherein the plurality of flags or unique elements include a backwardaccess flag and the media file includes a plurality of data fieldshaving a backward offset data field, the backward access flagreferencing the backward offset data field, the backward offset datafield having a pointer to a key-frame chunk and accessible by thede-multiplexer.
 35. The device of claim 34 wherein the de-multiplexersupplies the previous and next key-frame chunk to the video and audiodecoders to be decoded independently of any other chunks based on thepointer from the backward offset data field.